Our asthma research program involves both exposure assessment and prevention components, and focuses on the relationship between exposure to common indoor allergens and asthma prevalence and morbidity. We have worked with investigators at the CDC/NCHS to implement the allergen and asthma component of National Health and Nutrition Examination Survey (NHANES) 2005-2006. We collected bedroom dust, measured serum total and allergen-specific IgE and assessed asthma and allergy prevalence and morbidity in approximately 9000 individuals in the U.S. Analysis of this large data set will allow us to 1) estimate nationwide prevalence of indoor allergen and endotoxin exposures, 2) estimate nationwide prevalence of allergic sensitization to indoor, outdoor and food allergens, 3) estimate nationwide prevalence of allergic diseases, including asthma, and 4) investigate the complex relationships between allergen and endotoxin exposures, allergic sensitization and allergic diseases. The NHANES 2005-2006 is the first study that enabled both qualitative and a quantitative examination of population-level associations between allergic conditions and sensitization. The NHANES 2005-2006 data demonstrated that allergic sensitization in older patients with asthma is not uncommon. Asthma in patients 55 years or older was more strongly associated with sensitization to indoor allergen levels alone, whereas asthma in younger adults was associated with sensitization to both indoor and outdoor allergens. Using the data from this large, nationally representative sample of the U.S. population, we assessed whether phthalate metabolites were associated with allergic symptoms and sensitization, since environmental exposure to phthalates, particularly high molecular weight (HMW) phthalates, is suspected to contribute to allergy. We found that HMW phthalates, especially mono-benzyl phthalate (MBzP), were positively associated with allergic symptoms and sensitization in adults, but there was no strong evidence for phthalates and allergy in children aged 6-17 years. This study is the largest to date to evaluate the association of phthalates on allergic sensitization and symptoms in both adults and children. The NHANES data set has allowed for the investigation of many interesting relationships because the survey collected a large amount of health-related and environmental data. In fact, we demonstrated a novel relationship between allergic sensitization, as indicated by a broad panel of serum allergen-specific IgE (sIgE) and past myocardial infarction (MI). Serum sIgE was inversely associated with MI in the U.S. population in a manner independent of multiple coronary risk factors, suggesting a potential cardioprotective effect of allergic sensitization. To improve understanding of how various environmental exposures affect initiation of allergic responses that ultimately lead to allergic asthma, we examined the adjuvant activity of microbial products in house dust extracts. Our findings suggest that the bacterial protein flagellin (FLA) in household dust promotes the development of allergic asthma in mice by Toll-like receptor 5- dependent priming of allergic responses to indoor allergens. Consistent performance of allergen assays is essential to ensure reproducibility of exposure assessment procedures when investigating asthma and allergic disease. We participated in an international multi-center study that validated the performance characteristics a fluorescent multiplex array (MARIA) that quantifies several allergens in a single test. The results demonstrated a high level of reproducibility; the quantification of the allergens was reproducible both within and between laboratories. The MARIA methodology has the potential to significantly improve reproducibility and standardization of environmental allergen exposure assessment; the multiplex array not only increased the speed and efficiency of producing data on allergen exposure, but also improved sensitivity, accuracy and reproducibility of the measurements. To achieve a better understanding of the role that environmental exposures play in allergic sensitization and in the development of allergic diseases, we continue to investigate the complex relationships between allergen exposure, allergic sensitization, and disease in more detail. In addition to providing data on these relationships, the NHANES 2005-2006 will establish a second point-in-time estimate for evaluating allergen and endotoxin exposure trends in U.S. homes, first being established in the National Survey of Lead and Allergens in Housing, which we completed in collaboration with the Department of Housing and Urban Development.